7.2.2 XY-Format Images

The image-xy subtype represents an image as a sequence of
bitmaps, one for each plane of the image, in most-significant to
least-significant bit order. The following paragraphs describe the
additional CLX functions that can be used to access image-xy
objects.

image-xy-bitmap-list

image

Function

image

An image-xy object.

Returns and (with setf) changes the list of bitmap
planes for the image.